1. Field of the Invention
The present invention generally relates to a method for mounting a semiconductor device and, more particularly, to a method for fixing a semiconductor device having stud bumps to a mounting substrate by using an adhesive.
Recently, in order to reduce a mounting area of a mounting substrate to satisfy the demand of miniaturizing electronic equipment, semiconductor devices are reduced in their size and, thus, the pitches of their terminals are reduced. As a means of reducing the mounting area, there is a flip-chip mounting method to mount a bare chip on a mounting surface. In the flip-chip mounting method, the bare chip is generally fixed to the mounting substrate by an adhesive.
2. Description of the Related Art
There are the following two methods to apply an adhesive for mounting a semiconductor device in the flip-chip mounting method.
1) A semiconductor device is mounted to a mounting substrate after an adhesive is applied to the mounting substrate.
2) An adhesive is applied between a mounting substrate and a semiconductor device after the semiconductor device is mounted on the mounting substrate.
FIG. 1 is a flowchart of a mounting process for mounting a semiconductor device by using the above-mentioned method 1). FIG. 2 is an illustration for explaining the mounting process shown in FIG. 1.
In the mounting process shown in FIG. 1, after stud bumps 2 are formed on a semiconductor device 1, the stud bumps 2 are subjected to leveling so as to equalize the height of the stud bumps 2. The leveling is performed by pressing the stud bumps 2 against a hard material plate 3 such as a ceramics plate.
That is, as shown in FIG. 2-(a), the semiconductor device 1 having the stud bumps 2 is held by a tool 4 (step S1 of FIG. 2), and, then, the stud bumps 2 are pressed against the hard material plate 3. At this time, an electrically conductive adhesive 5 is previously applied to the hard material plate 3 so that the electrically conductive adhesive 5 is transferred to the stud bumps 2 during the leveling process (step S2).
Thereafter, the position recognition of the semiconductor mounting area of the mounting substrate 6 is performed (step S3). Then, as shown in FIG. 2-(b), an electrically non-conductive adhesive 7 is applied to the semiconductor mounting area of the mounting substrate 6 (step S4). The electrically non-conductive adhesive 7 is supplied so as to fill a space between the mounting surface of the semiconductor device 1 and the mounting substrate 6. That is, the electrically non-conductive adhesive 7 has the insulating property so as to protect the electrodes on the semiconductor device 1 and the mounting substrate 6.
On the other hand, the electrically conductive adhesive 5 is supplied so as to connect the stud bumps 2 to the lands 6a of the mounting substrate 6. Thus, the electrically conductive adhesive 5 provides a different function from the electrically non-conductive adhesive 7. After the electrically non-conductive adhesive 7 is applied to the semiconductor mounting area of the mounting substrate 6 as shown in FIG. 2-(c), the semiconductor device 1 is placed on the mounting substrate 6 as shown in FIG. 2-(d) and the electrodes of the semiconductor device 1 are bonded to the lands 6a of the mounting substrate 6 by applying a heat (step S5). The non-conductive adhesive 7 is also cured by the heat provided to bond the stud bumps 2.
FIG. 3 is a flowchart of a mounting process for mounting a semiconductor device by using the above-mentioned method 2). FIG. 4 is an illustration for explaining the mounting process shown in FIG. 3.
Similar to the method shown in FIG. 1, in the mounting process shown in FIG. 3, after the stud bumps 2 are formed on a semiconductor device 1, the stud bumps 2 are subjected to leveling so as to equalize the height of the stud bumps 2. The leveling is performed by pressing the stud bumps 2 against the hard material plate 3 such as a ceramics plate.
That is, as shown in FIG. 4-(a), the semiconductor device 1 having the stud bumps 2 is held by a tool 4 (step S11 of FIG. 3), and, then, the stud bumps 2 are pressed against the hard material plate 3. At this time, the electrically conductive adhesive 5 is previously applied to the hard material plate 3 so that the electrically conductive adhesive 5 is transferred to the stud bumps 2 during the leveling process (step S12).
Thereafter, as shown in FIG. 4-(b), the position recognition of the semiconductor mounting area of the mounting substrate 6 is performed (step S13). Then, as shown in FIG. 4-(c), the semiconductor device 1 is placed on the semiconductor mounting area of the mounting substrate 6 (step S14). In this state, the stud bumps 2 are electrically connected to the lands 6a of the mounting substrate 6 by the electrically conductive adhesive 5 on the stud bumps 2.
Thereafter, as shown in FIG. 4-(d), the electrically non-conductive adhesive 7 is supplied between the semiconductor 1 and the semiconductor substrate 6 (step S15).
In the above-mentioned mounting methods, the semiconductor device 1 is mounted to the mounting substrate 6 by the flip-chip mounting method by using the stud bumps 2. In a state in which the stud bumps 2 are formed on the semiconductor device 1, the height of the stud bumps 2 are not uniform. Accordingly, the leveling of the stud bumps 2 is performed so that all stud bumps 2 are put in contact with the respective lands 6a of the mounting substrate 6. In the conventional methods, the electrically conductive adhesive 5 is applied to the stud bumps 2 at the same time when the leveling is performed. Then, the semiconductor substrate 1 is fixed to the mounting substrate 6 mainly by the non-conductive adhesive 7.
As mentioned above, since the two kinds of adhesives, the electrically conductive adhesive and the electrically non-conductive adhesive, are used in the conventional flip-chip mounting method, the adhesives must be applied by the different processes which results in an increase in the number of processes. Accordingly, there is a problem in that the tact of the mounting process is long.
Additionally, there is a problem in that the electrically conductive adhesive is more expensive than the electrically non-conductive adhesive since the electrically conductive adhesive used for the conventional flip-chip mounting method is prepared by adding electrically conductive particles to an electrically non-conductive adhesive as a base.
Further, the facility cost of the semiconductor device mounting apparatus occupies a large weight in the entire facility cost relating with the flip-chip mounting. Accordingly, an increase in the manufacturing efficiency of the semiconductor device mounting apparatus greatly contributes the reduction in the manufacturing cost of the semiconductor device. In the flip-chip mounting method using the stud bumps, a thermosetting resin is used as the electrically non-conductive adhesive. Since the thermosetting resin takes a relatively long curing time such as 20 seconds to mount a single semiconductor device, there is a problem in that a manufacturing efficiency is not high.
It is a general object of the present invention to provide an improved and useful mounting method of a semiconductor device in which the above-mentioned problems are eliminated.
A more specific object of the present invention is to provide a mounting method of a semiconductor device, which reduces the number of processes and the cost for mounting the semiconductor device by reducing the number of kinds of adhesives necessary for mounting the semiconductor device.
In order to achieve the above-mentioned objects, there is provided according to one aspect of the present invention a method for mounting a semiconductor device having a plurality of stud bumps to a mounting substrate, the method comprising the steps of:
applying an electrically non-conductive adhesive to a planer surface of a hard material member;
attaching the semiconductor device to a bonding head;
leveling the stud bumps of the semiconductor device by pressing the stud bumps against the planer surface of the hard material member by the bonding head, and transferring a predetermined amount of the electrically non-conductive adhesive to a mounting area of the semiconductor device by separating the semiconductor device from the planer surface of the hard material member; and
fixing the semiconductor device to the mounting substrate by placing the semiconductor device on the mounting substrate and curing the electrically non-conductive adhesive on the mounting surface of the semiconductor device.
According to the above-mentioned invention, only the electrically non-conductive adhesive is used and the electrically conductive adhesive 5 used in the conventional mounting method is not used. That is, the electrically non-conductive adhesive can be applied to the semiconductor device instead of the electrically conductive adhesive in the conventional process in which the electrically conductive adhesive is applied to the semiconductor device. Accordingly, there is no need to perform the process for applying the electrically conductive adhesive, and, instead, the electrically non-conductive adhesive is applied to the semiconductor device simultaneously with the leveling of the stud bumps.
As mentioned above, by applying the electrically non-conductive adhesive to the semiconductor device while the leveling is performed, there is no need to perform the process for applying the electrically non-conductive adhesive alone. Therefore, the number of processes to be performed is reduced, and the tact of the mounting process is also reduced. Additionally, since the expensive electrically conductive adhesive is not used, the material cost can be reduced.
In one embodiment of the present invention, the electrically non-conductive adhesive may be in the form of a film so that the film is applied to the planet surface of the hard material member.
Additionally, there is provided according to another aspect of the present invention a method for mounting a semiconductor device having a plurality of stud bumps to a mounting substrate, the method comprising the steps of:
applying an electrically non-conductive adhesive to a planer surface of a hard material member, the electrically non-conductive adhesive made of a thermosetting resin;
attaching the semiconductor device to a bonding head;
leveling the stud bumps of the semiconductor device by pressing the stud bumps against the planer surface of the hard material member by the bonding head, and heating the bonding head so as to heat the electrically non-conductive adhesive via the semiconductor device, and transferring a predetermined amount of the electrically non-conductive adhesive to a mounting area of the semiconductor device by separating the semiconductor device from the planer surface of the hard material member; and
fixing the semiconductor device to the mounting substrate by placing the semiconductor device on the mounting substrate and thermally curing the electrically non-conductive adhesive on the mounting surface of the semiconductor device.
According to the above-mentioned invention, the electrically non-conductive adhesive is made of a thermosetting resin, and the heating of the bonding head heat is started from the step of applying the electrically non-conductive adhesive to the semiconductor device. Accordingly, the electrically non-conductive adhesive has been cured to a certain level when the semiconductor device is mounted to the mounting substrate. Thus, the curing time of the electrically non-conductive adhesive after the semiconductor device is mounted can be reduced.
Additionally, there is provided according to another aspect of the present invention a method for mounting a semiconductor device having a plurality of stud bumps to a mounting substrate, the method comprising the steps of:
applying an electrically non-conductive adhesive to a planer surface of a hard material member, the electrically non-conductive adhesive made of a thermosetting resin;
attaching the semiconductor device to a bonding head;
leveling the stud bumps of the semiconductor device by pressing the stud bumps against the planer surface of the hard material member by using the bonding head after being heated, and heating the bonding head so as to heat the electrically non-conductive adhesive via the semiconductor device and transferring a predetermined amount of the electrically non-conductive adhesive to a mounting area of the semiconductor device by separating the semiconductor device from the planer surface of the hard material member; and
fixing the semiconductor device to the mounting substrate by placing the semiconductor device on the mounting substrate and thermally curing the electrically non-conductive adhesive on the mounting surface of the semiconductor device.
According to the above-mentioned invention, the electrically non-conductive adhesive is made of a thermosetting resin, and the previously heated bonding head is used in the step of applying the electrically non-conductive adhesive to the semiconductor device. Accordingly, the electrically non-conductive adhesive has been cured to a certain level when the semiconductor device is mounted to the mounting substrate. Thus, the curing time of the electrically non-conductive adhesive after the semiconductor device is mounted can be reduced.
In the above-mentioned invention, the electrically non-conductive adhesive may be in the liquid state when being applied to the planer surface of the hard material member so that the electrically non-conductive adhesive on the planer surface has a uniform thickness. Accordingly, a predetermined amount of the electrically non-conductive adhesive can be applied to the semiconductor device by performing the leveling of the stud bumps.
Additionally, the semiconductor device may be separated from the hard material member after the electrically non-conductive adhesive becomes a gelatinized state by being heated in the process of transferring the electrically non-conductive material. Accordingly, an end surface of each of the stud bumps is exposed on the surface of the gelatinized electrically non-conductive adhesive. Additionally, the gelatinized electrically non-conductive adhesive has a strong adhesion force.
Since the gelatinized electrically non-conductive adhesive has a low fluidity, the semiconductor device can be fixed to the mounting surface by the electrically non-conductive adhesive by merely placing the semiconductor device on the mounting substrate. Thus, the mounting substrate can be subjected to another process immediately after the semiconductor device is mounted thereon.
Additionally, there is provided according to another aspect of the present invention a method for mounting a plurality of semiconductor devices to a mounting substrate by using a plurality of bonding heads, wherein the method uses the process of mounting according to the above mentioned methods according to the present invention, and the process of mounting is sequentially repeated with respect to each of the bonding heads in a manner in which the process of mounting with respect to one of the bonding heads are shifted by one step from the process of mounting with respect to another one of the bonding heads.
By performing the process of mounting by shifting the steps one by one from one bonding head to another bonding head, a higher productivity of the semiconductor device can be achieved than a case in which the mounting process is performed by using a single bonding head. In order to achieve a plurality of mounting processes by shifting the steps one by one, the tact of the processes of the steps must be substantially equal to each other. Otherwise the efficiency of the entire mounting process may be decreased. According to the above-mentioned invention, the curing time of the electrically non-conductive adhesive can be reduced or substantially eliminated, and, thereby, the tact of the step of fixing the semiconductor device to the mounting substrate including the curing of the electrically non-conductive adhesive can be substantially equal to the tact of other steps. Thus, the process of mounting can be performed by a plurality of bonding heads without decreasing the efficiency due to a difference in the tact.
Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings.